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Abstract:

A touchscreen electrode pattern constituted by wavy conductive lines,
each wavy conductive line includes multiple troughs of wave and multiple
crests of waves, wherein an interval between adjacent troughs of waves in
each wavy conductive line is larger than 1.5 times of a predetermined
value, and an amplitude difference between adjacent trough of waves and
crest of waves in each wavy conductive line is smaller than 1/3 times of
the predetermined value.

Claims:

1. An electrode pattern, comprising: a group of first electrodes; and a
group of second electrodes across said group of first electrodes, said
group of first electrodes and said group of second electrodes
constituting a mesh pattern; wherein at least one of said group of first
electrode and said group of second electrode is a group of wavy
conductive lines, each of said wavy conductive line comprises multiple
troughs of waves and multiple crests of waves, and an interval between
two adjacent said troughs of wave in each said wavy conductive line is
larger than 1.5 times of a predetermined value, and wherein an amplitude
difference between adjacent said trough of waves and said crest of waves
in each said wavy conductive line is smaller than 1/3 times of said
predetermined value.

2. The electrode pattern according to claim 1, wherein at least two of
said intervals in each said wavy conductive line are different, or at
least of two said amplitude differences in each said wavy conductive line
are different.

3. The electrode pattern according to claim 1, wherein the numbers of
said troughs of waves and said crests of waves in adjacent said wavy
conductive lines are different.

4. The electrode pattern according to claim 1, wherein two adjacent said
wavy conductive lines in said group of first electrodes have different
wavy shapes, and two adjacent said wavy conductive lines in said group of
second electrodes have different wavy shapes.

5. The electrode pattern according to claim 1, wherein said predetermined
value is a pixel pitch of a display corresponding to said electrode
pattern.

6. The electrode pattern according to claim 5, when said electrode
pattern is disposed on said display, the angle between said electrode
pattern and the pixel pattern of said display ranges from 30.degree. to
60.degree..

7. The electrode pattern according to claim 1, wherein said mesh pattern
is a non-periodic pattern with irregular mesh cell.

8. The electrode pattern according to claim 1, wherein the pitch of said
wavy conductive lines is at least 20 times greater than the width of said
wavy conductive lines.

9. The electrode pattern according to claim 1, wherein the pitch of said
wavy conductive lines ranges from 150 microns to 6000 microns.

10. The electrode pattern according to claim 1, wherein the width of said
wavy conductive lines ranges from 1 micron to 10 microns.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to a touchscreen, and more
particularly, to a touchscreen with a mesh-like electrode pattern which
is capable of eliminating the moire phenomenon.

[0003] 2. Description of the Prior Art

[0004] Touchscreen displays are able to detect a touch within the active
or display area, such as detecting whether a finger is present pressing a
fixed-image touchscreen button or detecting the presence and position of
a finger on a larger touchscreen display. Some touchscreens can also
detect the presence of elements other than a finger, such as a stylus
used to generate a digital signature, select objects, or perform other
functions on a touchscreen display.

[0005] The Use of a touchscreen as part of a display allows an electronic
device to change a display image, and to present different buttons,
images, or other regions that can be selected, manipulated, or actuated
by touch. Touchscreens can therefore provide an effective user interface
for cell phones, GPS devices, personal digital assistants (PDAs),
computers, ATM machines, and other devices.

[0006] Touchscreens use various technologies to sense touch from a finger
or stylus, such as resistive, capacitive, infrared, and surface acoustic
sensors. A capacitive touch screen, for example, may include an insulator
coated with a transparent conductor such as indium tin oxide (ITO) or
transparent conductive polymers such as PEDOT (polyethylene
dioxythiophene) in a particular pattern. When an object, such as a finger
or a stylus, touches the surface of the screen, there may be a change in
capacitance. This change in capacitance may be sent to a controller for
processing to determine where the touch occurred on the touch screen.

[0007] While transparent conductors such as ITO may be used for
electrodes, however, since the transparent conductive layer has high
resistance of 100 ohms/square or more, the sensitivity is lowered when
the display device is manufactured in a large scale, and as the size of
screen is increased, the cost of the ITO film is rapidly increased.
Accordingly, it is not easy to perform commercialization thereof.

[0008] In order to overcome this conventional issue, there is an effort to
implement enlargement by using an opaque metal pattern having high
conductivity. When the electrode pattern is made of the metal, electric
conductivity is excellent, and demand and supply is smooth. In the case
in which the electrode pattern is made of the metal such as copper,
silver or other conductive materials, the electrode pattern should be
formed in a mesh structure in a micrometer (μm) unit in order to
prevent users from recognizing the electrode pattern and make the
electrodes substantially invisible to the naked eye.

[0009] However, when the electrode pattern of the touch panel is formed in
the mesh structure having regular and constant intervals, there is a
problem in that period characteristics of the metal mesh electrode
pattern of the touch panel may cause interference with a periodic pixel
pattern of the IC circuit or a regular pattern structure of another
optical film, such as a black matrix pattern of a color filter included
in an image display device overlapped with each other, thereby causing a
so-called "moire" phenomenon. Herein, the moire means an interference
pattern formed when two or more regular and repeating patterns overlap.

[0010] The occurrence of moire makes it difficult to see a displayed image
of the display, and thereby deteriorates the visual operability or
usability of the touch screen device. Categorized broadly, moire may be
low-frequency moire in which large patterns consecutively appear, or
high-frequency moire in which small patterns consecutively appear. In
particular, low-frequency moire will make the display difficult to be
viewed.

SUMMARY OF THE INVENTION

[0011] The present invention has been made in an effort to address the
above-mentioned situation and circumstances that can occur in the
conventional technologies. A touchscreen includes sensing electrode
elements is provided and distributed across an active area of a
substrate, and the touchscreen overlays a display. The sensing electrode
elements form a mesh pattern configured to avoid creating moire patterns
by utilizing irregular wavy, zig-zag or randomized line configurations.

[0012] The objective of the present invention is to provide a mesh
electrode pattern constituted by wavy conductive lines. Each wavy
conductive line includes multiple troughs of wave and multiple crests of
waves. An interval between adjacent troughs of waves in each wavy
conductive line is larger than 1.5 times of a predetermined value. An
amplitude difference between adjacent trough of waves and crest of waves
in each wavy conductive line is smaller than 1/3 times of the
predetermined value.

[0013] According to the present invention, by superposing the regular
pattern of other panel components with the touchscreen having
above-mentioned specific irregular mesh electrode patterns, it is
possible to inhibit the moire phenomenon.

[0014] These and other objectives of the present invention will no doubt
become obvious to those of ordinary skill in the art after reading the
following detailed description of the preferred embodiment that is
illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are included to provide a further
understanding of the embodiments, and are incorporated in and constitute
a part of this specification. The drawings illustrate some of the
embodiments and, together with the description, serve to explain their
principles. In the drawings:

[0016] FIG. 1 is an exemplary cross-sectional view of a touch
position-sensing panel which overlies a display in accordance with one
embodiment of the present invention;

[0017] FIG. 2 is a plan view showing a state in which a pixel pattern
formed in a display is overlapped with the pattern of mesh electrode of
FIG. 1;

[0018] FIG. 3 is a plan view individually showing a mesh electrode pattern
in accordance with one preferred embodiment of the present invention;

[0019] FIG. 4 is a plan view individually showing a mesh electrode pattern
in accordance with another embodiment of the present invention;

[0020] FIG. 5 is a plan view individually showing a mesh electrode pattern
in accordance with still another embodiment of the present invention;

[0021] FIG. 6 illustrates a single wavy conductive line in the mesh
electrode pattern in accordance with one preferred embodiment of the
present invention; and

[0022] FIG. 7 illustrates a single zig-zag conductive line in the mesh
electrode pattern in accordance with another embodiment of the present
invention.

[0023] It should be noted that all the figures are diagrammatic. Relative
dimensions and proportions of parts of the drawings have been shown
exaggerated or reduced in size, for the sake of clarity and convenience
in the drawings. The same reference signs are generally used to refer to
corresponding or similar features in modified and different embodiments.

DETAILED DESCRIPTION

[0024] In the following detailed description of the present invention,
reference is made to the accompanying drawings which form a part hereof
and is shown by way of illustration and specific embodiments in which the
invention may be practiced. These embodiments are described in sufficient
details to enable those skilled in the art to practice the invention.
Other embodiments may be utilized and structural, logical, and electrical
changes may be made without departing from the scope of the present
invention. The following detailed description, therefore, is not to be
taken in a limiting sense, and the scope of the present invention is
defined by the appended claims.

[0025] FIG. 1 illustrates an exemplary touch position-sensing panel 1
which overlies a display 2. In the illustrated example, the panel 1
includes an insulating substrate 3 having two opposing faces 3a and 3b.
Although touch sensors may implement other types of touch sensing, for
discussion purposes, the drawing shows an example of a structure that may
be used to implement a mutual capacitance type touch sensitive panel.

[0026] The panel 1 includes a number of lower electrodes 4 and a number of
upper electrodes 5 provided on opposite faces 3a and 3b of the substrate
3. The electrodes 4, which may be on face 3b, may be arranged in one
direction and the electrodes 5, which may be on face 3a, may be arranged
in a direction different from the direction of electrodes 4. Other
conductive tracks may also be provided on the opposing faces 3a and 3b of
the substrate 3. Such other conductive tracks may provide drive and sense
connections to the electrodes 4 and 5. The substrate 3 may be provided
adjacent to the display 2 such that electrodes 4 are arranged between the
display 2 and the substrate 3. An adhesive layer 6 comprised of an
optically clear adhesive may be disposed between the electrodes 4 and a
transparent covering sheet 7. An adhesive layer 8 comprised of an
optically clear adhesive may be disposed between the electrodes 5 and a
transparent covering sheet 9. A gap may be formed between the display 2
and the transparent covering sheet 7. As an example and not by way of
limitation, the display 2 underneath the touch sensor may be a liquid
crystal display (LCD), a light-emitting diode (LED) display, a
LED-backlight LCD, or other suitable display.

[0027] The transparent covering sheet 7 and the adhesive layer 6 may
encapsulate all electrodes 4 and any other conductive tracks formed on
face 3b of the substrate 3. The transparent covering sheet 9 and the
adhesive layer 8 may encapsulate all electrodes 5 and any other
conductive tracks formed on face 3a of the substrate 3. The encapsulation
of the electrodes 4 and 5 and any other conductive tracks, may provide
protection from physical and environmental damage. In some examples,
portions of the conductive tracks may be exposed to provide connection
points for connection to external drive circuitry.

[0028] In the mutual capacitance example, electrodes 4 may be drive
electrodes provided on face 3b of the substrate 3, and electrodes 5 may
be sense electrodes provided on the opposing face 3a of the substrate 3.
Capacitive sensing channels may be formed by capacitive coupling nodes in
the localized regions around where electrodes 4 and 5 cross over each
other and are separated by the substrate 3.

[0029] The electrode pattern 4 and 5 serve to generate a signal at the
time of a touch by a user to allow a controller to recognize a touch
coordinate. Here, the electrode patterns 4 and 5 may be made of copper
(Cu), aluminum (Al), gold (Au), silver (Ag), titanium (Ti), palladium
(Pd), chromium (Cr), and other metals used in conductive wiring. In
addition, the electrode pattern may be formed by a plating process or a
depositing process using a sputter.

[0030] In some examples, the sense electrodes may be patterned in fine or
micro wires to allow most of the light emitted from the display and
incident on the sense electrode layer to pass through the electrode layer
between the fine metal wires. The fine lines may be no more than 20
microns wide. An exemplary range may be 1-5 microns. Narrower lines have
reduced visibility to the naked eye. By forming electrodes 4 or 5 from
micro conductive lines, the position-sensing panel may be formed such
that no more than about 10% of the active area is covered by the metal
lines of the electrodes. Less coverage of the active area allows for
greater transparency of the position-sensing panel and reduces visibility
of the electrodes to the human eye. It may also reduce perceptible
darkening or other loss of display quality. An exemplary coverage may be
less than 5%.

[0031] In some examples, the electrodes 4 may be formed of a clear
conductive material and the electrodes 5 may be formed of narrow
conductive lines. In other examples, the electrodes 4 may be formed of
narrow conductive lines and the electrodes 5 may be formed of a clear
conductive material.

[0032] In an example where other conductive tracks in addition to the
electrodes 4 and 5 are provided on the substrate 3, the other conductive
tracks may also be formed of a clear conductive material or narrow
conductive lines, in a manner similar to the electrode layers 4 and 5. In
an example where the other conductive tracks, or parts of the other
conductive tracks, lie outside a visible region of the display 2, the
light-transmissibility of the other conductive tracks is of no concern.

[0033] Since the electrode pattern 4 and 5 are formed on the transparent
substrate 3, the transparent substrate 3 needs to have support force
capable of supporting the electrode pattern 4 and 5 and transparency
capable of allowing a user to recognize an image provided from the image
display device. In consideration of the support force and the
transparency described above, the transparent substrate 3 may be made of
polyethylene terephthalate (PET), polycarbonate (PC), poly methyl
methacrylate (PMMA), polyethylene naphthalate (PEN), polyethersulfone
(PES), a cyclic olefin polymer (COC), a triacetylcellulose (TAC) film, a
polyvinyl alcohol (PVA) film, a polyimide (PI) film, polystyrene (PS),
biaxially oriented polystyrene (BOPS; containing K resin), glass,
tempered glass, or the like, but is not necessarily limited thereto.

[0034] Configuration of touchscreen elements relative to the line or pixel
configuration of the display 2 is important in some applications to
reduce moire patterns, as line configurations that cover regular or
repeating patterns of pixels can create interference or moire patterns in
the touchscreen display assembly. It is therefore desirable in the
embodiment to configure electrodes being irregular or being oriented at
angles that do not cause such interference with the underlying display
assembly.

[0035] For this reason, FIG. 2 shows a state in which a pixel pattern 12
(thick lines) formed in the display 2 is overlapped with the pattern of
mesh electrode 5 (thin lines) of FIG. 1. As shown in FIG. 2, an array of
pixels 12 included in the display 2 that each displays at least a portion
of an image may be visible through conductive lines of the mesh electrode
pattern 5. In a case where the mesh electrode pattern 5 is disposed on a
display 2 having such a pixel pattern 12, the conductive lines in the
mesh electrode pattern 5 may orient to certain oblique angles with
respect to the horizontal and vertical arrangement directions of the
pixels in the display. The angle between the imaginary line of mesh
pattern 5 and pixel pattern 12 may range from 30° to 60°,
preferably 30° to 40°.

[0036] As shown in FIG. 2, the mesh electrode pattern 5 has an irregular,
non-periodic shape, while a pixel pattern 12 (or a black matrix pattern
of a color filter in backlight module) included in the display 2 (ex. a
liquid crystal display (LCD), or the like) has the translation symmetry
with periodic lattice structures. As a result, even though the mesh
electrode pattern 5 and the pixel pattern 12 are disposed to be
overlapped with each other, generation of an interference phenomenon may
be minimized, such that the moire phenomenon may be prevented. In
addition, due to the irregularity of the mesh electrode pattern 5, the
generation of an interference phenomenon may also be minimized even
though the mesh electrode pattern 5 and the pixel pattern 12 rotates to
different directions with respect to each other.

[0037] Furthermore, the opening ratio per unit area of the mesh electrode
pattern 5 may be maintained to be constant, such that the touch panel may
secure uniform electric conductivity and visibility.

[0038] Please refer now to FIG. 3, which illustrates a plan view
individually showing a mesh electrode pattern according to the preferred
embodiment of the present invention. As shown in FIG. 3, in this
embodiment, the mesh electrode pattern 5 is composed of a group of first
electrodes 21 crossing a group of second electrodes 22 in wavy line
fashion, such that the conductive grid or mesh pattern is made up of an
array of substantially irregular shaped mesh cells. Each first electrode
21 and second electrode 22 is non-linear, wavy conductive lines (ex. in a
sinusoidal fashion) arranged respectively at a first pitch L1 and a
second pitch L2. The finger's influence on multiple drive and receive
conductive lines (i.e. touchscreen electrodes) enables the touchscreen
display to detect the vertical and horizontal position of a finger on the
touchscreen display with very good accuracy, well beyond simply
determining in which of the vertical and horizontal regions the finger is
located. To achieve this result, the line pitch here is configured
anticipating a fingerprint that is approximately 8 mm in diameter. The
first pitch L1 and the second pitch L2 may be selected within a range of
150 μm to 6000 μm (6.0 mm). The line width of the first electrodes
21 and second electrodes 22 may be selected within a range of 1 μm to
10 μm.

[0039] When using fine line metal mesh electrodes that are 5 μm in
width, the pitch between the conductive lines would be several decuples
to several hundred times of the width of the lines, resulting in a very
low line density and a relatively large width from line to line. Both the
low density and relatively large spacing between lines reduce the
likelihood of producing visible moire patterns when overlaying a display
having a regularly repeating pixel configuration. In other examples, the
line pitch is at least 20, 50, 100, or 150 times greater than the line
width.

[0040] In addition, the group of first electrodes 21 and the group of
second electrodes 22 in the mesh electrode pattern 5 form a large number
of lattice intersection points. Each electrode is formed in a wavy line
shape containing at least one curve/wave between the intersections.

[0041] The irregular or sinusoidal shape of the conductive lines as shown
in FIG. 4 may reduce diffraction effects which may be encountered if
straight conductive lines are used. Such diffraction effects may result
in the appearance of "starburst" patterns when a touch position-sensing
panel is subject to bright ambient light. Such diffraction effects may
result in color shifting, changing the apparent colors of liquid crystal
display (LCD) elements of a display visible through a touch
position-sensing panel, and may obscure the image being displayed.

[0042] Moreover, the irregular or sinusoidal shape of the conductive lines
may also reduce the visibility of reflections from the conductive lines
when a touch position sensing panel is illuminated by light from a point
illumination source, such as the sun on a clear day. The sinusoidal shape
of the conductive lines may tend to distribute or disperse the apparent
position on the touch position sensing panel of such reflections, and so
may minimize the perceived visibility of repetitive reflection patterns.
Such repetitive reflection patterns are readily perceived by the human
eye.

[0043] Please refer to FIG. 4, which illustrates a plan view individually
showing a mesh electrode pattern according to another embodiment of the
present invention. In this embodiment, the mesh electrode pattern 5 is
composed of a plurality of first electrodes 21 and second electrodes 22.
Each of the electrodes 21 and 22 is a non-linear conductive line.
However, each first electrode 21 has the same line wavy shape, while
adjacent second electrodes 22 have different wavy shapes.

[0044] Please refer to FIG. 5, which illustrates a plan view individually
showing a mesh electrode pattern according to still another embodiment of
the present invention. In this embodiment, the mesh electrode pattern 5
is composed of a plurality of first electrodes 21 and second electrodes
22. However, each first electrode 21 is in straight line shape, while
each second electrode 22 is in non-linear wavy shape. Furthermore,
adjacent second electrodes 22 have different wavy shapes.

[0045] Please refer now to FIG. 6, which illustrate a single conductive
line in the mesh electrode pattern according to one preferred embodiment
of the present invention. In this embodiment, each conductive line,
including first electrode 21 and second electrode 22, in the mesh
electrode pattern 5 is a wavy structure. The numbers of waves in adjacent
conductive lines are different. The interval D between two adjacent
troughs of waves in each conductive line is preferably configured to be
larger than 1.5 times of a predetermined value. Furthermore, the
amplitude difference H between adjacent crest and through of waves in
each conductive line is preferably configured to be smaller than 1/3
times of said predetermined value. The predetermined value is preferably
the pixel pitch of the underlying display 2. The pixel pitch is the
distance between the centers of two adjacent pixels in the display 2. The
wavy conductive line in the mesh electrode pattern 5 should fulfill the
requirement that at least two intervals D among multiple intervals in all
wavy conductive lines are different, or at least two amplitude
differences H among multiple amplitude differences in all wavy conductive
lines are different.

[0046] Of course, in an alternative embodiment, the requirement may be at
least two intervals D in multiple intervals D of one or more wavy
conductive lines are different, or at least two amplitude differences H
in multiple amplitude differences H of one or more wavy conductive lines
are different.

[0047] In still another embodiment, the requirement may be the intervals D
between two adjacent troughs of wave in a number of the wavy conductive
lines being configured larger than 1.5 times of a predetermined value,
and the amplitude differences H between adjacent crest and through of
wave in a number of the wavy conductive lines being configured smaller
than 1/3 times of said predetermined value.

[0048] Please refer now to FIG. 7, which illustrate a single conductive
line in the mesh electrode pattern according to another embodiment of the
present invention. In this embodiment, unlike the one shown in FIG. 6,
the non-linear conductive line is in zig-zag shape rather than wavy
shape. The intervals D between two adjacent vertices in the same side is
configured larger than 1.5 times of a predetermined value, and the
amplitude differences H between adjacent vertices in opposite sides is
configured smaller than 1/3 times of said predetermined value.

[0049] In the embodiment, wavy lines are used to avoid long linear
stretches of fine metal line, reducing the probability of causing
interference patterns. Similarly, the fine metal lines in zig-zag form
may also break up the long linear stretches of parallel lines. The
conductive lines in above fashions would follow a more randomized
pattern. Furthermore, the randomized electrode line may be shifted
laterally from line to line to break up vertical regularity in the
electrode pattern; the amount of shifting from line to line can in itself
be randomized to further suppress the ability of groups of lines to cause
a moire effect. Fractal-based or other irregular shapes are used in
further embodiments to achieve a similar effect.

[0050] Those skilled in the art will readily observe that numerous
modifications and alterations of the device and method may be made while
retaining the teachings of the invention. Accordingly, the above
disclosure should be construed as limited only by the metes and bounds of
the appended claims.